The research involves: (1) studies on the significance of the "early region" of the SV40 genome for the maintenance of the transformed phenotype; and (2) studies on human and mouse cells biochemically transformed to the thymidine kinase (TK) positive phenotype by herpesvirus TK genes. Mouse kidney lines transformed by an SV40tsA mutant, which are temperature-sensitive for growth, and variant heat-resistant lines derived from it, as well as re-revertants, are being studied. The number and sites of SV40 DNA sequences integrated, the localization of T antigens by CF and IF, and the formation of radioisotope labeled small and large T antigens are being studied. Double mutants with ts lesions in the distal part of the A region and with deletions in the early part of the A region will be isolated and characterized. The DNAs and restriction nuclease DNA fragments from various herpes-viruses are being used to biochemically transform TK-negative human and mouse cells. Sites of integration will be compared by isozyme, and chromosome antigens (HANA) detected in the biochemically transformed cells will be purified and characterized.